Solid propellant having a ferrocene containing polyester fuel binder

ABSTRACT

Ferrocene Polyesters that are prepared by the equation: HO2C(R)CO2H+HO(R)OH -&gt; HO2C ((R)-CO2(R)-O2C)xRCO2H wherein HO(R)-OH is a difunctional alcohol and HO2C(R)CO2H is a difunctional acid, and (R) belongs to the group comprising alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or alkynyl radicals which may be substituted by one or more ferrocenyl groups.

United States Patent Combs, Jr. et al.

[ 51 May 27, 1975 SOLID PROPELLANT HAVING A FERROCENE CONTAININGPOLYESTER FUEL BINDER Inventors: Charles S. Combs, Jr., Huntsville;Charles I. Ashmore, Owens Cross Roads, both of Ala.

Assignee: Thiokol Corporation, Bristol, Pa.

Filed: May 9, 1973 Appl. N0.: 358,568

' Related U.S. Application Data 7 V a Division of Ser. No. 730,633, May20, 1968, abandoned.

U.S. Cl. 149/19.2; 149/19.5; 149/20 Int. Cl C06d 5/06 Field of Search149/19, 20, 38, 44, 19.2,

[56] References Cited UNITED STATES PATENTS 3,598,850 8/1971 Dewey149/19 X 3,739,004 6/1973 Ponder et a1. 149/19 X PrimaryExaminerBenjamin R. Padgett Attorney, Agent, or Firm--Thomas W. Brennan[57] ABSTRACT 4 Claims, No Drawings SOLID PROPELLANT HAVING A FERROCENECONTAINING POLYESTER FUEL BINDER This a division of application Ser. No.730,633 now abandoned filed May 20, 1968.

BACKGROUND OF THE INVENTION l. Field of the Invention Ferrocene andferrocene derivatives have been used to give improved combustionstability and increased burn rates. One of the long recognized problemsassociated with the use of these compounds has been the relatively highmobility and vapor pressure of ferrocene and ferrocene derivatives.Associated with this problem is the fact that this high mobility andhigh vapor pressure limits the amount of ferrocene compound which can beused in a practical propellant since losses through volatility andbleeding are severe at high levels of incorporation of organometalliccompounds. In some instances nonvolatile solid ferrocene derivatives areused to give decreased mobility and volatility. When the object of theadditive is to obtain high burning rates, large amounts of ferrocenecompounds must be used. However, large amounts of solid ferrocene orsolid ferrocene derivatives are used to the detriment of practicalprocessability. This invention solves the problems associated withvolatility and bleeding out of ferrocene derivatives by incorporatingthe catalysts as an agent which is chemically bonded into the propellantbinder. The catalytic agent is thereby prevented from being lost exceptby rupture of a bond by a chemical reaction.

2. Description of the Prior Art One of the greatest problems to beovercome in this particular field of endeavor is producing eitherchemically or mechanically, procedures that will increase the burningrate of a composite solid propellant in a solid propellant rocket motorto increase the efficiency of the solid propellant rocket motor duringoperational flights. One of the procedures previously followed relatedto particle size of the particular oxidizer that was used in thecomposite solid propellant and it had been found that it was necessaryto use very small particles of oxidizer in the composite solidpropellant in order to achieve high burning rates.

In order to overcome the extra expense involved in producing the fineparticles of oxidizer, the instant invention was developed whereby highburning rates were made available without the extra expense involved inproducing oxidizer having very small particle sizes.

SUMMARY OF THE INVENTION This invention relates, therefore, to the areaof composite solid propellants and solid propellant binders in whichferrocene types compounds are used to give stable combustion andincreased burning rates, and more specifically to polyester propellantbinders in which organometallic moieties are included as integral partsof the binder.

One of the most important advantages which accrue from the instantinvention is that in addition to the ferrocene unit which is chemicallybonded into the propellant binder, other solid or liquid ferrocenecompounds may be added up to levels which induce problems withprocessing, bleeding or volatility. In this manner much larger amountsof burning rate catalysts may be incorporated in the composite solidpropellant, and

extremely high burning rates may be achieved without the problemspreviously encountered.

The primary object of this invention, therefore, is to provide ferrocenepolyesters that will give composite solid propellants stable combustionand increased burning rates.

Another object of the invention is to provide ferrocene polyesterbinders in which organometallic moieties are included as integral partsof the binder.

While only certain objects and advantages of the invention have been setforth, it is believed that other objects and advantages will becomeapparent to one skilled in the art from the following detaileddescription and discussion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Liquid plasticizable, curableferrocene containing polyesters have been prepared conveniently and ingood yield. In general, the polymers are prepared from the appropriateacid and the appropriate glycol according to the reaction shown:

in which one of the comonomers is a difunctional alcohol of the generalstructure I-IO(R)OI-I in which (R) is an alkyl, alkenyl, cycloalkyl,cycloalkenyl, aryl, or alkynyl group, and may be substituted by one ormore ferrocenyl or substituted ferrocenyl groups, and in which thecarbon chain may contain or may be substituted by groups containingsulfur, oxygen, halogen, nitrogen, or metallic atoms, and in which oneof the comonomers is a difunctional acid of the general structure:

in which (R) is as described above and in which one or more comonomerscontain at least one ferrocenyl or substituted ferrocenyl group as anintegral part of one of the repeating units. The polyester is terminatedby hydroxyl or carboxyl groups, or both, according to the conditions ofthe reaction. In the instance of termination by carboxylic acid groups,the polyester is cured by means of common aziridinyl or epoxide-typecuring agents. When the polyester is terminated by hydroxyl groups, thepolyester is cured by means of common isocyanate or carboxylic acidanhydride curing agents.

The preparation of the ferrocene containing polyester embodying theinvention is illustrated by the following:

EXAMPLES A mixture of (hydroxymethyhferrocene (21.6 g., 0.100 mole) andmercaptosuccinic acid (30.0 g., 0.200 mole) contained in 200 ml. ofwater was stirred and brought to the reflux temperature, after which itwas allowed to stand until it reached room temperature. The resultingsolid was recovered by vacuum filtration and washed several times withwater. The solid was taken up in ether and extracted several times with5 percent aqueous sodium bicarbonate. The extractions were combined,gravity filtered, and neutralized by addition to 10 percent hydrochloricacid. The precipitate which resulted was extracted with ether. Theethereal solution was washed with water until neutral to litmus. Theether layer was dried over anhydrous magnesium sulfate, filtered(gravity) and the solvent removed in vacuo.(Ferrocenylmethylthio)succinic acid, M.P. l77l79, was recovered in anamount equal to 78 percent (27.7 g) of the theoretical yield. Infraredanalysis agreed with the structural assignment:

where Fc represents ferrocenyl.

The (ferrocenylmethylthio)succinic acid prepared above (11.48 g, 0.033mole), 2-butene-l,4-diol (2.64 g., 0.030 mole), and p-toluenesulfonicacid monohydrate (0.07 g., 0.5 percent of the other constituents byweight) were placed in 80 ml. of toluene and allowed to reflux for fourhours. The orange solution was filtered, while hot, through glass woolinto approximately 250 ml. of n-hexane. The polymer separated to thebottom on standing, and the supernatent liquid was decanted. The polymerwas taken up in acetone and poured into n-hexane after which theprecipitationdecantation procedure was repeated. The polymer was takenup in acetone and the solution poured through a column containing asmall amount of alumina (acid washed). Residual polymer was eluted withmore acetone, the solutions combined, and the solvent removed in vacuowith heat (approximately 40C). A clear, orange, viscous but mobilepolymer was recovered in an amount equal to 76 percent (9.94 g.) of thesum of the monomers less the theoretical amount of water evolved.Infrared analysis agreed with the structural assignment:

carboxyl content was found by titration to be 0.1076 eq/ 100 g. for thepolymer obtained by this preparation. Assuming the functionality toequal 2, the molecular weight is calculated to be 1,859. The followinganalysis was obtained, by ashing, for iron: found Fe, 14.7 percent;calculated Fe, 14.4 percent.

In a similar manner a mixture of 1, S-pentanediol and ethylene glycol(75/25 by mole percent) was allowed to react with(ferrocenylmethylthio)succinic acid to afford a ferrocene containingpolyester which exemplitied a product prepared from a reaction in whichmore than one polyfunctional alcohol was used.

The resulting polyester was similar in appearance and physicalproperties to the previously described polymer.

It was also determined that an excellent solid propellant compositioncomprising the following ingredients could be provided: 2 to 90 percentof a solid oxidizer such as ammonium perchlorate, ammonium nitrate orRDX; 2 to 40 percent of a polymeric binder, as embodied in the instantinvention, to 50 percent of a metallie fuel, 0 to 25 percentofa'dd-itives such as plasticizers, burning rate catalysts, curecatalysts, combustion stabilizers, and 0 to 30 percent of a non-metalcontaining polymeric fuel binder such as a hydrocarbon polymer.

It was also determined that tris-(2 methylaziridinyl)- phosphine oxideand dibutylcarbutol formal could be used in the foregoing composition toprovide excellent results as a curing agent and as a plasticizerrespectively. It was also determined that the solid propellantcomposition possessed good physical properties.

It is to be understood, therefore. that while the present invention hasbeen described by means of the foregoing examples, many obviousmodifications and variations will occur to those with ordinary skill inthe art and it is to be further understood that such variations andmodifications may be adhered to without departing from the originalspirit of the invention, and the scope of the appended claims.

What is claimed is:

1. In a solid propellant composition comprising;

an oxidizer selected from the group consisting of ammonium perchlorate,ammonium nitrate and RDX, a metallic fuel and a polymeric binder, theimprovement comprising:

said binder comprising a ferrocene polyester consisting essentially ofthe reaction product of 2-butane- 1,4-diol and (ferrocenylmethylthio)succinic acid.

2. A solid Propellant composition as in claim 1, wherein the polymericbinder is wherein x is equal to a number resulting in moleculare weightof 1.859.

3. A composite solid propellant composition comprising a solid ozidizerselected from the group consisting of ammonium perchlorate, ammoniumnitrate and RDX, a metallic fuel and a polymeric binder, the improvementcomprising:

said polymeric binder being a ferrocene polyester consisting essentiallyof the reaction product of 1,5-pentanediol and (ferrocenylmethylthio)succinic acid.

4. In a solid propellant composition comprising a solid oxidizerselected from the group consisting of ammonium perchlorate, ammoniumnitrate and RDX, a metallic fuel and a polymeric binder, the improvementcomprising:

said polymeric binder being a ferrocene polyester consisting essentiallyof the reaction product of 1,5-pentanediol, ethylene glycol, and(ferrocenylmethylthio) succinic acid.

1. IN A SOLID PROPELLANT COMPOSITION COMPRISING, AN OXIDIZER SELECTEDFROM THE GROUP CONSISTING OF AMMONIUM PERCHLORATE, AMMONIUM NITRATE ANDRDX, A METALLIC FUEL AND A POLYMERIC BINDER, THE IMPROVEMENT COMPRISING:SAID BINDER COMPRISING A FERROCENE POLYESTER CONSISTING ESSENTIALLY OFTHE REACTION PRODUCT OF 2-BUTANE-1,4-DIOL AND (FERROCENYLMETHYLTHIO)SUCCINIC ACID.
 2. A solid Propellant composition as in claim 1, whereinthe polymeric binder is HO2C-CH2CH (SCH2Fc) CO2CH2CHCHCH2O2xCH2CH(SCH2Fc)CO2H wherein x is equal to a number resulting inmoleculare weight of 1.859.
 3. A composite solid propellant compositioncomprising a solid ozidizer selected from the group consisting ofammonium perchlorate, ammOnium nitrate and RDX, a metallic fuel and apolymeric binder, the improvement comprising: said polymeric binderbeing a ferrocene polyester consisting essentially of the reactionproduct of 1,5-pentanediol and (ferrocenylmethylthio) succinic acid. 4.In a solid propellant composition comprising a solid oxidizer selectedfrom the group consisting of ammonium perchlorate, ammonium nitrate andRDX, a metallic fuel and a polymeric binder, the improvement comprising:said polymeric binder being a ferrocene polyester consisting essentiallyof the reaction product of 1,5-pentanediol, ethylene glycol, and(ferrocenylmethylthio) succinic acid.